1. Field of the Invention
The invention relates to electro-optical displays, and particularly to an improved pixel configuration and control circuits to provide different pixel configurations for different pixel midtone sequences and thus minimize optical aberrations, such as stairstepping and fuzzy black-white transitions.
2. Description of the Prior Art
Picture elements (pixels) may have simple binary configurations typified by the off/on lamp binary of the theater marquee. Pixel configurations have progressed from the binary 1,0 to midtone configurations based upon three-unit (0,1,2) or other multi-unit side-by-side placement of picture element components.
A typical two-bit specified side-by-side tone pixel configuration in the prior art is:
______________________________________ Bit Value Pixel ______________________________________ 0,0 012 White White White 0,1 0-12 White Black White 1,0 --012 Black Black White 1,1 ---012 Black Black Black ______________________________________
Multi-unit pixel configurations may define pixels with many variations of color and gray tone shading. Resolution may be increased as a function of increased use of storage.
Data compression systems involving various gray scale filtering techniques are discussed under the subheading "Description of the Prior Art" in copending U.S. patent application of W. B. Pennebaker and K. S. Pennington, Ser. No. 429,658, filed Sept. 30, 1982, entitled "DATA FILTER AND COMPRESSION APPARATUS AND METHOD."
Multi-unit pixel configurations permit the production of complex displays with midtones ranging from black through several colors and shades of gray to white--but multi-unit pixel configurations have a tendency to develop optical aberrations due to random patterns in open fields and at the transition edges where tones change, for example where black meets white. Such aberrations may appear as lines or stairsteps and are generally undesirable; even in the absence of other aberrational optical patterns it is an undesirable aberration for a black-white transition to be fuzzy.